目录
- 介绍
- 常用注解
- 实际测试
介绍
Spring Cache
是一个框架,实现了基于注解的缓存功能,只需要简单地加一个注解,就能实现缓存功能。
Spring Cache提供了一层抽象,底层可以切换不同的cache实现。具体就是通过CacheManager
接口来统一不同的缓存技术。
CacheManager是Spring提供的各种缓存技术抽象接口。
针对不同的缓存技术需要实现不同的CacheManager:
常用注解
在Spring Boot项目中,使用缓存技术只需在项目中导入相关缓存技术的依赖包,并在启动类上使用@EnableCaching开启缓存支持即可。
例如,使用Redis作为缓存技术,只需要导入spring-boot-starter-data-redis的Maven坐标即可。
实际测试
使用Spring Cache(默认缓存ConcurrentMapCacheManager
)
创建Spring Boot项目,使用MybatisX插件生成对应的mapper、service、实体类等,导入相关依赖,修改配置文件,创建数据库
pom.xml如下:
<?xml version="1.0" encoding="UTF-8"?> <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <parent> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-parent</artifactId> <version>2.4.5</version> <relativePath/> <!-- lookup parent from repository --> </parent> <groupId>com.itheima</groupId> <artifactId>cache_demo</artifactId> <version>1.0-SNAPSHOT</version> <properties> <java.version>1.8</java.version> </properties> <dependencies> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> <scope>compile</scope> </dependency> <dependency> <groupId>org.projectlombok</groupId> <artifactId>lombok</artifactId> <version>1.18.20</version> </dependency> <dependency> <groupId>com.alibaba</groupId> <artifactId>fastjson</artifactId> <version>1.2.76</version> </dependency> <dependency> <groupId>commons-lang</groupId> <artifactId>commons-lang</artifactId> <version>2.6</version> </dependency> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <scope>runtime</scope> </dependency> <dependency> <groupId>com.baomidou</groupId> <artifactId>mybatis-plus-boot-starter</artifactId> <version>3.4.2</version> </dependency> <dependency> <groupId>com.alibaba</groupId> <artifactId>druid-spring-boot-starter</artifactId> <version>1.1.23</version> </dependency> </dependencies> <build> <plugins> <plugin> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-maven-plugin</artifactId> <version>2.4.5</version> </plugin> </plugins> </build> </project>
application.yml如下:
server:
port: 8080
spring:
application:
#应用的名称,可选
name: cache_demo
datasource:
druid:
driver-class-name: com.mysql.cj.jdbc.Driver
url: jdbc:mysql://localhost:3306/cache_demo?serverTimezone=Asia/Shanghai&useUnicode=true&characterEncoding=utf-8&zeroDateTimeBehavior=convertToNull&useSSL=false&allowPublicKeyRetrieval=true
username: root
password: 123456
mybatis-plus:
configuration:
#在映射实体或者属性时,将数据库中表名和字段名中的下划线去掉,按照驼峰命名法映射
map-underscore-to-camel-case: true
log-impl: org.apache.ibatis.logging.stdout.StdOutImpl
global-config:
db-config:
id-type: ASSIGN_ID
数据库SQL如下:
/* Navicat Premium Data Transfer Source Server : Aiw Source Server Type : MySQL Source Server Version : 50528 Source Host : localhost:3306 Source Schema : cache_demo Target Server Type : MySQL Target Server Version : 50528 File Encoding : 65001 */ SET NAMES utf8mb4; SET FOREIGN_KEY_CHECKS = 0; -- ---------------------------- -- Table structure for user -- ---------------------------- DROP TABLE IF EXISTS `user`; CREATE TABLE `user` ( `id` bigint(20) NOT NULL, `name` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NULL DEFAULT NULL, `age` int(11) NULL DEFAULT NULL, `address` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NULL DEFAULT NULL, PRIMARY KEY (`id`) USING BTREE ) ENGINE = InnoDB CHARACTER SET = utf8mb4 COLLATE = utf8mb4_general_ci ROW_FORMAT = Compact; -- ---------------------------- -- Records of user -- ---------------------------- INSERT INTO `user` VALUES (1568896554487369729, 'Aiw', 22, '湖北省'); SET FOREIGN_KEY_CHECKS = 1;
在启动类上添加@EnableCaching
注解
package com.itheima; import lombok.extern.slf4j.Slf4j; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; import org.springframework.cache.annotation.EnableCaching; @Slf4j @SpringBootApplication @EnableCaching // 开启缓存注解功能 public class CacheDemoApplication { public static void main(String[] args) { SpringApplication.run(CacheDemoApplication.class,args); log.info("项目启动成功..."); } }
创建UserController
package com.itheima.controller; import com.itheima.entity.User; import com.itheima.service.UserService; import lombok.extern.slf4j.Slf4j; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.cache.CacheManager; import org.springframework.cache.annotation.CacheEvict; import org.springframework.cache.annotation.CachePut; import org.springframework.cache.annotation.Cacheable; import org.springframework.web.bind.annotation.*; import java.util.List; import java.util.Objects; @RestController @RequestMapping("/user") @Slf4j public class UserController { @Autowired private CacheManager cacheManager; @Autowired private UserService userService; /** * CachePut:将方法返回值放入缓存 * value:缓存的名称,每个缓存名称下面可以有多个key * key:缓存的key */ @CachePut(value = "userCache", key = "#user.id") @PostMapping public User save(User user) { userService.save(user); return user; } /** * CacheEvict:清理指定缓存 * value:缓存的名称,每个缓存名称下面可以有多个key * key:缓存的key */ @CacheEvict(value = "userCache", key = "#p0") //@CacheEvict(value = "userCache",key = "#root.args[0]") //@CacheEvict(value = "userCache",key = "#id") @DeleteMapping("/{id}") public void delete(@PathVariable Long id) { userService.removeById(id); } //@CacheEvict(value = "userCache",key = "#p0.id") //@CacheEvict(value = "userCache",key = "#user.id") //@CacheEvict(value = "userCache",key = "#root.args[0].id") @CacheEvict(value = "userCache", key = "#result.id") @PutMapping public User update(User user) { userService.updateById(user); return user; } /** * Cacheable:在方法执行前spring先查看缓存中是否有数据,如果有数据,则直接返回缓存数据;若没有数据,调用方法并将方法返回值放到缓存中 * value:缓存的名称,每个缓存名称下面可以有多个key * key:缓存的key * condition:条件,满足条件时才缓存数据 * unless:满足条件则不缓存 */ @Cacheable(value = "userCache", key = "#id", unless = "#result == null") @GetMapping("/{id}") public User getById(@PathVariable Long id) { return userService.getById(id); } @Cacheable(value = "userCache", key = "#user.id + '_' + #user.name") @GetMapping("/list") public List<User> list(User user) { return userService.lambdaQuery() .eq(Objects.nonNull(user.getId()), User::getId, user.getId()) .eq(Objects.nonNull(user.getName()), User::getName, user.getName()) .list(); } }
以上不同写法均等价
使用ApiPost进行接口测试
打断点调试,发送请求,可以看到已存入缓存
该缓存底层基于Map实现,默认ConcurrentHashMap基于内存,重启服务会清空缓存数据
使用Spring Cache(redis缓存RedisCacheManager
)
导入Maven坐标
<dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-cache</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-data-redis</artifactId> </dependency>
修改配置文件
server:
port: 8080
spring:
application:
#应用的名称,可选
name: cache_demo
datasource:
druid:
driver-class-name: com.mysql.cj.jdbc.Driver
url: jdbc:mysql://localhost:3306/cache_demo?serverTimezone=Asia/Shanghai&useUnicode=true&characterEncoding=utf-8&zeroDateTimeBehavior=convertToNull&useSSL=false&allowPublicKeyRetrieval=true
username: root
password: 123456
redis:
host: localhost
port: 6379
# password: root@123456
database: 0
cache:
redis:
time-to-live: 1800000 #设置缓存过期时间(单位:秒),可选
mybatis-plus:
configuration:
#在映射实体或者属性时,将数据库中表名和字段名中的下划线去掉,按照驼峰命名法映射
map-underscore-to-camel-case: true
log-impl: org.apache.ibatis.logging.stdout.StdOutImpl
global-config:
db-config:
id-type: ASSIGN_ID
启动项目,再次请求接口
启动redis命令行窗口,查看
当请求不存在的id时,不会执行缓存操作(@Cacheable注解的unless条件起作用)
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